A positive test could mean that hospitals and doctors would have to eat the charges if patients under the influence don't make good on the bills. To sidestep the problem, the hospitals often don't screen patients for alcohol use.

You might think that an organization like Mothers Against Drunk Driving would support these so-called alcohol-exclusion laws. But the opposite is true. MADD opposes them. The reason? The laws put a damper on testing for intoxication, and that's a critical step in preventing drunken driving.

Testing helps gauge scope of the problem and can aid prosecution of offenders, says Nick Ellinger, a spokesman for MADD. "If someone is involved in a crash, and if they have alcohol in their system, the doctor can institute screening and intervention, and set them on road to not doing it in the future."

Screening can also lead someone to get counseling. And that's important. A recent study published in the Annals of Emergency Medicine found that patients who were identified as problem drinkers and given a single 7-minute counseling session significantly reduced the number of drinks they consumed in a week over the next year. The counseling also cut down on the episodes of binge drinking and driving after drinking compared with a group that received standard care.

The National Association of Insurance Commissioners, an early backer of alcohol-exclusion laws, developed a model statute that states could use as a blueprint for their own laws. In 2001, the organization switched gears and recommended against such laws. Since then, at least 15 states have repealed their laws.